The oral cavity represents a unique body part that is in contact with the external world and therefore constantly encounters a vast diverse of microbes. Herpesviruses are significant resident oral pathogens in humans. However, little is known about how the host senses and responds to herpesviruses during primary infection, latency and reactivation in the oral cavity, especially in regards to the innate immune system. Coexistence of a virus and its immunocompetent host entails a delicate balance between viral replication and host clearance. Elucidating the interactions between the innate immune system and herpesviruses will provide insights to how the balance is accomplished and regulated. A mouse model of murine gammaherpesvirus-68 (MHV-68) infection provides an excellent system to explore virus-host interactions in the oral cavity for several reasons. First, following oral administration, MHV-68 replicates in the oronasal cavity and the salivary gland. Second, an amenable genetic system is available to mutagenize the MHV-68 viral genome. Third, MHV-68 infects a variety of laboratory strains of mice, which allows the role of cellular genes during viral infection to be studied in vivo. [unreadable] [unreadable] The long-term goal of our discovery driven approach is to determine the role of viral and cellular proteins in virus-associated pathogenesis by employing knock-out mice and a collection of MHV-68 mutant viruses. The MHV-68 genome is randomly disrupted by an insertion of a transponson. There are 32 viral ORFs that are not required for replication in fibroblast cells and potentially involved in modulating virus-host interactions. The object of this exploratory R21 application is to define the in vivo sensing and defending role of TLR and its signaling pathway using a mouse model of oral MHV-68 infection. Furthermore, we will systematically screen viral genes that are capable of inhibiting the activation of anti-viral responses in cells, an essential step for understanding virus-host interactions. [unreadable] [unreadable] [unreadable]